The present invention relates broadly to systems for controlling ventilation curtains in a livestock enclosure such as a poultry house. More specifically, the present invention relates to a hydrostatically powered system for automatically dropping the curtains open in the event of a power failure or in response to other life-threatening conditions.
As will be appreciated by those familiar with the poultry industry, modern poultry farmers must focus on producing as large a number of marketable chickens in as short a time as possible in order to obtain commercially meaningful returns. Hence, the poultry farmer generally fills each of his poultry houses as close to capacity as possible. For example, a typical poultry house several hundred feet in length commonly houses from 1,500 to 2,000 chickens.
However, dense population in a poultry house may create life-threatening conditions for the fowl. For example, chickens tightly crowded together are extremely vulnerable to suffocation and overheating when air flow in the house is not properly controlled. To encourage healthy air flow, poultry houses are typically provided with large screen windows or wire-covered side walls. Air flow is regulated in part by selectively covering or uncovering the side walls or windows with impermeable curtains. Typically, the curtains are mounted on the house floor or the bottom of the windows. The curtains may be selectively drawn upwardly over the side wall by a conventional system of winch-controlled pulleys. Most houses are also equipped with a forced air ventilation system, typically comprising one or more electric fans.
It will be appreciated that if a power failure disables the electric fans and/or the curtain controls, the temperature inside the house may rapidly rise to a dangerous level. Moreover, air quality can rapidly diminish, as ammonia builds up in the air. Chickens may quickly succumb unless adequate ventilation is immediately supplied. Moreover, if inadequate air is supplied, high levels of carbon dioxide accumulate near the floor, resulting in rapid suffocation of the chickens. Thus, it is critical to the poultry farmer to assure that air flow is properly regulated at all times. Power outage or other failure of air control systems must therefore be immediately detected and corrected to prevent undesired losses to the flock.
In the prior art known to us numerous auxiliary temperature control systems have been proposed for use in poultry houses. More specifically, a wide variety of poultry house curtain control systems are known. For example, U.S. Pat. No. 3,915,377 issued to Sutton on Oct. 28, 1975 discloses a curtain control device for poultry houses. The device comprises a temperature sensor and a sensor for detecting a power failure in combination with an electrically-powered curtain winch system. An auxiliary power system comprising a battery is associated with the winch system. When a power failure is sensed, an alarm sounds, and the control system is automatically switched to battery power. The battery-powered system burns through a cord, which results in release of the winch, so that the curtains freely drop to the floor to provide ventilation.
U.S. Pat. No. 4,428,278 issued Jan. 31, 1984 to Sutton discloses a similar emergency curtain control system wherein a cord is directly interconnected with the winding mechanism of the curtain control. An electromagnetic system is employed to cause the curtain control cord to automatically release when a power outage or other dangerous condition is sensed.
Newell, U.S. Pat. No. 3,802,479, issued Apr. 9, 1974, discloses a system for raising and lowering poultry house curtains. When life-threatening conditions such as the presence of excessive ammonia, changes in relative humidity, and dangerously high temperature are sensed, the window curtains are automatically raised to enhance ventilation. Of lesser relevance is U.S. Pat. No. 3,511,299 issued to Newell on May 12, 1970, which also relates to poultry house curtain control systems. Smith, U.S. Pat. No. 3,973,173 issued Aug. 3, 1976 describes a system for electromagnetically controlling poultry house curtains. Electromagnetic controls release a cord which is mechanically coupled to the handle of the curtain winch, whereby the curtains automatically drop when a power failure is sensed.
Other mechanical means for controlling curtains in livestock enclosures are disclosed in the following U.S. Pat. Nos.: Dubie, 3,042,001, issued Jul. 3, 1962; 3,429,298 issued to Thomason on Feb. 25, 1969; 3,474,761 issued Oct. 28, 1969 to Thomason; 3,571,973 issued to Roberts on Mar. 23, 1971; and, White Patent 3,669,350, issued Jun. 13, 1972. In addition, various prior patents are directed generally to auxiliary control systems, such as Pearson, U.S. Pat. No. 4,129,811 issued Dec. 12, 1978; U.S. Pat. No. 4,602,739, issued Jul. 29, 1986 to Sutton; Siccardi, U.S. Pat. No. 4,369,040, issued Jan. 18, 1983; and, U.S. Pat. No. 4,632,304, issued Dec. 30, 1986 to Newell.
One obvious drawback associated with battery-powered auxiliary systems is that batteries fail if not regularly charged. No electromechanical or electronic control system known to us provides adequate independence from conventional electric power sources. The mechanical release systems known to us typically involve a series of complex couplings, which also require careful maintenance and are therefore relatively vulnerable to failure. The results of failure of the auxiliary ventilating system may be disastrous. Prior art systems also can jam when their actuating strings get tangled. Known prior art units do not allow the curtains and the winch to be adjusted when the system is engaged.
Hence it is desired to provide a highly reliable curtain control system which operates independent of conventional electric sources, and which may be conveniently installed into existing curtain systems.